Nobody will buy the hardware if they can't commit to supporting the software. In a previous role, I was responsible for advising purchasing decisions for my company's laptop fleet. The Surface X (Arm edition) looked cool, but we weren't willing to take the risk, because at the time Microsoft had far worse transitional support than they do now. It's gotten better, but no one in their right mind is going to make the kind of volume purchases that actually drive adoption until they demonstrate they are in it for the long haul. It's a chicken and egg problem, and Microsoft doesn't care what hardware you are using, so long as it is running Windows or using (expensive) Windows services.